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Re: [Qemu-devel] ARM v4t support

From: Filip Navara
Subject: Re: [Qemu-devel] ARM v4t support
Date: Mon, 30 Nov 2009 10:10:56 +0100

On Sun, Nov 29, 2009 at 10:12 PM, Rob Landley <address@hidden> wrote:
> On Sunday 29 November 2009 03:57:37 Filip Navara wrote:
>> On Sun, Nov 29, 2009 at 8:00 AM, Rob Landley <address@hidden> wrote:
>> > On Friday 27 November 2009 05:35:26 Filip Navara wrote:
>> >> On Fri, Nov 27, 2009 at 12:17 PM, Vincent Sanders <address@hidden>
>> >
>> > wrote:
>> >> > I appear to be unable to take a hint, your silence on this patch in
>> >> > the past probably ought to have been a clue. however this will be the
>> >> > last time I bother to try and get anything merged so you wont have to
>> >> > be disturbed again.
>> >> >
>> >> > The attached patch adds V4t support to the ARM emulation, its pretty
>> >> > much the same as the last time it was posted. It is correct in
>> >> > everything it does to the best of my knowledge however you will as
>> >> > usual no doubt find a corner case it does not cover and reject it.
>> >>
>> >> I have already sent more complete patch for ARM7TDMI emulation:
>> >>
>> >> http://www.mail-archive.com/address@hidden/msg17205.html
>> >> http://patchwork.ozlabs.org/patch/36841/
>> >
>> > That's a link to an archive that gives you html but not a raw patch.
>> >  (Huh, it says you sent it to the list but I'm not finding it in my mail
>> > folder. Rummage, rummage, rummage...  Ah, your original patch was dated
>> > December 31 1969.)
>> Yep, a bug in TortoiseGIT that was later fixed.
>> > Ok, dug it up, applied it, booted an -M versatilepb kernel built with an
>> > armv4tl compiler that I'm assured works for real armv4tl hardware, and I
>> > get no boot messages if I say "-cpu arm7tdmi", but it boots fine if I
>> > don't say that.
>> >
>> > Let's try my armv4l setup (which I've booted on real armv4tl hardware,
>> > albeit with a different kernel .config but qemu hasn't got a board
>> > emulation for the Tin Can Tools Hammer, last I checked...)  That's an
>> > OABI which doesn't depend on the Thumb extensions...
>> >
>> > Nope, that's armv4 OABI, and I've tested the output of that compiler on
>> > real hardware, albeit with a different kernel .config.
>> >
>> > Your patch does not work for me.  Is there a kernel .config change I need
>> > to do for this?  Looking in the kernel kconfig stuff, the only way to
>> > select arm7tdmi is to disable MMU support.  Is this a nommu processor?
>> >  (I know there are armv4t processors _with_ mmu...)
>> It is nommu processor, so I would be surprised to see any of the
>> kernels running. Unfortunately I don't have a ready-to-use kernel
>> .config file for it, since I never even tried it with Linux.
> Did you add any armv4t processors with mmu?  I believe the actual hardware I
> tested was an ARM920T.  Vincent's patch claims to add arm920T, I tested yours
> because you claimed it was "more complete".

No, I didn't. My patch is more complete in the underlying ARM V4 bits,
not in the formal definitions of the processor models. Adding ARM920T
is matter of adding these two lines to target-arm/cpu.h (as in
Vincent's patch):

#define ARM_CPUID_ARM920T     0x41129200
{ ARM_CPUID_ARM920T, "arm920t"},

and then adding the processor definition into helper.c:

    case ARM_CPUID_ARM920T:
        set_feature(env, ARM_FEATURE_ABORT_BU);
        set_feature(env, ARM_FEATURE_CP15);
        env->cp15.c0_cachetype = 0x0d172172;
        env->cp15.c1_sys = 0x00000078;

> I guess I should go test vincent's.
>> > What kernel .config, -M, and -cpu and  did you use to test an armv4t
>> > system image with your patch?
>> -M at91pes (which is included in other patches from around the same
>> time, but was never merged)
> "Included in other patches"...  How _many_ other patches?  And how far is
> "around"?


The repository is desperately in need of rebasing, but I still didn't
find a time to do so.

> If you'd like to resubmit them as a batch, I can try coming up with a kernel
> .config.  (And a uClibc .config since I haven't actually tried a nommu system
> yet.)

I'll resubmit them soon and maybe merge some of the AT91SAM9 work,
including the ARM920T cpu.

Best regards,
Filip Navara

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